THE VARIABLE LIGHT-CURVE OF THE ECLIPSING SYMBIOTIC STAR AR-PAVONIS

Photometric measurements in four colours and visual observations of th e eclipsing symbiotic star AR Pav covering almost 7 cycles of the 604. 5 day orbit between 1982 and 1993 are presented. Together with publish ed data they us allow to determine improved orbital ephemeries. The sh ape of the eclipse is analysed. Its width is found to be shorter than previously estimated. The brightness and colour changes during the orb ital cycle are discussed. AR Pav is found to be highly variable out of eclipse. In some cycles a marked peak appears which is absent in othe rs. Several explanations for the out-of-eclipse variability are sugges ted, the most satisfying of which is a brightness modulation due to va riation in the mass transfer rate from the red giant to the hot compon ent.